P 4. Waves and their uses P 8 minutes 8 marks Answer all questions using any and all resources. Page of 38
Q. Diagram shows four of the seven types of wave in the electromagnetic spectrum. Diagram J K L Visible light Infrared Microwaves Radio waves (a) The four types of electromagnetic wave named in Diagram above are used for communication. (i) Which type of electromagnetic wave is used when a traffic signal communicates with a car driver? () Which type of electromagnetic wave is used to communicate with a satellite in space? () Gamma rays are part of the electromagnetic spectrum. Which letter, J, K or L, shows the position of gamma rays in the electromagnetic spectrum? Draw a ring around the correct answer. J K L () Page 2 of 38
(c) Diagram 2 shows an infrared wave. Diagram 2 (i) Which one of the arrows, labelled A, B or C, shows the wavelength of the wave? Write the correct answer, A, B or C, in the box. () Draw a ring around the correct answer to complete the sentence. shorter than The wavelength of infrared waves is the same as the wavelength of radio waves. longer than () (d) Mobile phone networks send signals using microwaves. Some people think the energy a person s head absorbs when using a mobile phone may be harmful to health. (i) Scientists have compared the health of people who use mobile phones with the health of people who do not use mobile phones. Which one of the following statements gives a reason why scientists have done this? Tick ( ) one box. To find out if using a mobile phone is harmful to health. To find out if mobile phones give out radiation. To find out why some people are healthy. () Page 3 of 38
The table gives the specific absorption rate (SAR) value for two different mobile phones. The SAR value is a measure of the maximum energy a person s head absorbs when a mobile phone is used. Mobile Phone SAR value in W/kg X 0.28 Y.35 A parent buys mobile phone X for her daughter. Using the information in the table, suggest why buying mobile phone X was the best choice. (2) (Total 8 marks) Q2. A person can see an image of himself in a tall plane mirror. The diagram shows how the person can see his hat. (a) Which point, A, B or C, shows the position of the image of his hat? Write the correct answer, A, B or C, in the box. () On the diagram, use a ruler to draw a light ray to show how the person can see his shoe. (3) Page 4 of 38
(c) Which one of the words in the box is used to describe the image formed by a plane mirror? Draw a ring around the correct answer. imaginary real virtual () (Total 5 marks) Q3. Diagram shows a longitudinal wave being produced in a stretched spring. (a) A longitudinal wave has areas of compression and areas of rarefaction. Mark with the letter C, one area of compression shown in Diagram. () Diagram 2 shows the apparatus a teacher uses to demonstrate that sound can be reflected. (i) Using a ruler, draw on Diagram 2 to show how sound from the loudspeaker is reflected by the sheet of metal to the sound sensor. The teacher replaced the sheet of metal with a sheet of glass. When he did this, the reading on the sound level meter went down. Suggest why. (2) () Page 5 of 38
(iii) The teacher changed the output from the loudspeaker to increase the amplitude of the sound wave produced. What effect, if any, does this increase of amplitude have on the loudness of the sound? Draw a ring around the correct answer. makes the sound quieter does not change the loudness of the sound makes the sound louder () (iv) The loudspeaker produces a sound wave at a frequency of 850 Hz. The wavelength of the sound wave is 0.4 m. Calculate the speed of the sound wave. Use the correct equation from the Physics Equations Sheet. Show clearly how you work out your answer. Speed =... m/s (2) (c) Music concerts are sometimes performed in sports halls. The concerts can be spoilt because of the sound reflected from the floor and walls. What word is used to describe a reflected sound?... () Page 6 of 38
(d) The graph shows how the percentage of sound reflected from the floor and from the walls of a large room can be reduced by carpets and by curtains. (i) Over which range of frequencies do curtains reduce the percentage of sound reflected the most? Tick ( ) two boxes. from 250 Hz to 750 Hz from 750 Hz to 250 Hz from 250 Hz to 750 Hz () Page 7 of 38
The manager of a sports hall plans to use the hall for regular music concerts. He has enough money to buy either carpet or curtains, but not both. To improve the sound an audience hears, it would be better to hang curtains on the walls rather than laying a carpet over the floor. Use the data in the graph to explain why. (2) (Total marks) Q4. Small sailing boats can be fitted with a passive radar device. The device increases the chance that the small boat will be seen on the radar screen of a large ship. The radar transmitter on the large ship emits microwaves. (a) Microwaves and radio waves are both part of the electromagnetic spectrum. How are microwaves different from radio waves?...... () How fast do microwaves travel through the air or a vacuum compared to radio waves?... () Page 8 of 38
(c) The diagrams show the position of a passive radar device on a small boat and the internal construction of one type of passive radar device. Microwaves can be absorbed, reflected or transmitted by different materials and types of surface. Explain what happens to the microwaves from the ship s transmitter when they reach the passive radar device............. (2) Page 9 of 38
(d) Each type of passive radar device has an RCS value. The larger the RCS value, the easier it is for a small boat fitted with the device to be detected. An independent group of scientists measured the RCS values of 4 different types of device. The RCS value for each device was measured in the same room using the same equipment. (i) Why are the walls of the room covered in a material that absorbs the waves emitted by the radar transmitter? () Why is it important to use the same room and the same equipment? () (iii) Why is it important that the measurements are made by an independent group of scientists? () Page 0 of 38
(e) The movement of a small boat causes the mast and device to lean over, therefore the RCS values were measured at different angles. The table gives the RCS values obtained by the scientists. Device Angle X 0 5 0 5 A.4.6.7.8 B 4.7 2.6 2.3.9 C 9.3 3.3.9. D 4.5 4.8 5.0 4.6 (i) Describe how the RCS values for device A are different to the RCS values for device B. (2) The scientists recommended that a passive radar device fitted to a small boat should have: the largest possible RCS value an RCS value consistently above 2.0 Which one of the devices, A, B, C or D, would you recommend that someone fits to their boat? Give a reason for your answer.... () (Total 0 marks) Page of 38
Q5. The diagram shows a model used to demonstrate an illusion known as Pepper s Ghost. A small light bulb and thin sheet of glass are put inside a box. The thin sheet of glass acts as a mirror. Although the light bulb is switched on, a student looking into the box cannot see the bulb. What the student does see is a virtual image of the bulb. (a) Use a ruler to complete a ray diagram to show how the image of the light bulb is formed. Mark and label the position of the image. (4) Page 2 of 38
The image seen by the student is virtual. Why?...... () (Total 5 marks) Q6. (a) Microwaves and visible light are two types of electromagnetic wave. Both can be used for communications. (i) Give two properties that are common to both visible light and microwaves.... 2... (2) Name two more types of electromagnetic wave that can be used for communications.... and... () Wi-Fi is a system that joins computers to the internet without using wires. Microwaves, with a wavelength of 2.5 cm, are used to link a computer to a device called a router. Microwaves travel through the air at 300 000 000 m/s. Use the equation in the box to calculate the frequency of the microwaves used to link the computer to the router. wave speed = frequency wavelength Show clearly how you work out your answer and give the unit.......... Frequency =... (3) Page 3 of 38
(c) Wi-Fi is used widely in schools. However, not everyone thinks that this is a good idea. A politician commented on the increasing use of Wi-Fi. He said: I believe that these systems may be harmful to children. However, one group of scientists said that there is no reason why Wi-Fi should not be used in schools. These scientists also suggested that there is a need for further research. (i) Suggest what the politician could have done to persuade people that what he said was not just an opinion. () Why did the group of scientists suggest that there is a need for further research? () (Total 8 marks) Q7. (a) A lorry has an air horn. The air horn produces sound waves in the air. (i) Use one word to complete the following sentence. Sound waves cause air particles to.... () The air horn produces sound waves at a constant frequency of 420 Hz. The wavelength of the sound waves is 0.80 m. Calculate the speed of the sound waves. Use the correct equation from the Physics Equations Sheet. Speed =... m/s (2) Page 4 of 38
A person standing at the side of the road, as the lorry goes past, hears the sound from the air horn change pitch. (i) What determines the pitch of a sound? Draw a ring around the correct answer. amplitude frequency loudness () As the lorry moves away from the person, the air horn continues to produce sound waves with a wavelength of 0.80 m. What is the wavelength of the sound waves the person heard? Draw a ring around the correct answer. shorter than 0.8 m equal to 0.8 m longer than 0.8 m () (iii) The sound waves the person heard from the moving air horn are different to the sound waves the air horn produced. What name is given to this effect? Draw a ring around the correct answer. diffraction Doppler refraction () (Total 6 marks) Q8. (a) Scientists have observed that the wavelengths of the light from galaxies moving away from the Earth are longer than expected. (i) What name is given to this observation? () Draw a ring around the correct answer to complete each sentence. light can be stretched. This observation gives scientists evidence that galaxies are changing colour. the Universe is expanding. () Page 5 of 38
(iii) There is a pattern linking the size of the observed increase in the wavelengths of light from a galaxy and the distance the galaxy is from the Earth. Which one of the graphs, L, M or N, shows the correct pattern? Write the correct answer in the box. () Observations help scientists answer questions about the Universe. Scientists cannot answer every question. Which one of the following questions cannot be answered by scientists? Tick ( ) one box. How old is the Universe? Why was the Universe created? How fast does light travel through the Universe? () (Total 4 marks) Page 6 of 38
Q9. The diagram shows a teacher using a loudspeaker to demonstrate an important effect. The loudspeaker produces a note of constant frequency and is swung around in a circle. (a) As the loudspeaker moves towards the students, the frequency of the note heard by the students increases. What happens to the note heard by the students as the loudspeaker moves away from them?...... () The teacher is using the demonstration to model the red-shift in light observed from most distant galaxies. (i) Which part of the demonstration: represents a moving galaxy? is like the red-shift? (2) Page 7 of 38
Which one of the following statements gives the main reason why models are used in science? Put a tick ( ) in the box next to your answer. Models can help to explain an effect or theory. Models can prove that a theory is correct. Models can prove that a theory is wrong. () (c) Red-shift provides evidence to support the theory that the Universe began from a very small initial point. What name is given to this theory?... () (Total 5 marks) Q0. The big bang theory is one theory explaining the origin of the Universe. (a) The graphs X, Y and Z, show how the size of the Universe may have changed with time. Which graph would the big bang theory suggest is correct? Write your answer, X, Y or Z, in the box. Explain the reason for your answer............. (3) Page 8 of 38
In 948, an alternative to the big bang theory, called the steady state theory, was developed. The steady state theory suggested that the Universe, although expanding, has always existed without a beginning in time. (i) Complete the following sentence by drawing a ring around the correct line in the box. The measurement of red-shift in the light from distant galaxies provides evidence only the big bang theory. to support only the steady state theory. both the big bang and steady state theories. () In 965, scientists rejected the steady stat theory in favour of the big bang theory. Suggest what might cause scientists to stop supporting one theory and to start supporting an alternative theory. () (Total 5 marks) Q. (a) The Big Bang theory uses red-shift as evidence to explain the beginning of the Universe. How does the red-shift from distant galaxies provide evidence for the beginning of the Universe?.................. (3) Page 9 of 38
Cosmic microwave background radiation (CMBR) is a type of electromagnetic radiation. CMBR fills the Universe. It was first discovered in 965 by two astronomers called Penzias and Wilson. (i) What do scientists believe is the origin of CMBR? () Why was the discovery of CMBR so important to the scientists believing the Big Bang theory to be correct? () (iii) How is the wavelength of CMBR likely to change, if at all, over the next billion years? Give a reason for your answer. (2) (Total 7 marks) Q2. The Big Bang theory is one theory of the origin of the Universe. (a) (i) Explain what is meant by the Big Bang theory. (2) The light arriving from distant galaxies provides scientists with evidence to support the Big Bang theory. Explain how. (2) Page 20 of 38
At a meeting held in 2005, a group of scientists claimed that new data had been collected that showed the Big Bang theory to be wrong. Other scientists said that there was no reason to doubt the Big Bang theory. What should scientists do when a theory does not appear to be supported by new data?............ (2) (c) Scientists can answer many questions about the Universe, but not the question: Suggest a reason why this question cannot be answered by scientists....... () (Total 7 marks) Page 2 of 38
M. (a) (i) (visible) light accept visible microwaves J (c) (i) B shorter than (d) (i) To find out if using a mobile phone is harmful to health any two from: (X has a) low(er) SAR value it refers to mobile phone accept has a low(er) rate (maximum) energy absorbed (by the head) is less accept energy emitted (by phone) is less accept radiation for energy (if mobiles are harmful) less likely to cause harm accept will not cause harm accept it is safer 2 [8] M2. (a) C reflection at the mirror of ray from shoe to person s eye may be drawn freehand angle of incidence = angle of reflection judged by eye a ruler must have been used arrow to show correct direction on either incident or reflected ray only one arrow needed but if more drawn must be no contradiction both incident and reflected ray must be shown Page 22 of 38
(c) virtual [5] M3. (a) letter C clearly marking a compression accept C at any point in a compression if more than one letter C marked all must be correct (i) straight continuous line drawn from loudspeaker to metal to sound sensor judge by eye angle I = angle R judge by eye ignore any arrows on lines less sound reflected accept energy for sound or (some) sound passes through the glass accept (some) sound absorbed by the glass (iii) (iv) makes the sound louder v = f λ 340 allow mark for correct substitution ie 850 0.4 provided no subsequent step shown 2 (c) echo (d) (i) from 250 Hz to 750 Hz Page 23 of 38
curtains reduce (percentage of) sound reflected more (than carpet) accept curtains absorb more sound (than carpet) for all frequencies (shown) accept for both marks an answer in terms of walls having a larger (surface) area to reflect sound and curtains reducing the amount of reflected sound more (than carpet) answers less noisy or walls / curtains have a larger area gain mark only do not accept curtains are cheaper [] M4. (a) higher frequency general properties / uses are neutral or shorter wavelength do not accept different frequency / wavelength / energy or greater energy (c) the same (speed) accept they travel at the speed of light pass through / transmitted by the plastic / casing reflected by the metal / plates do not accept bounce / deflected etc for reflected if neither marking point scores an answer reflected (back to boat / from the device) scores mark (d) (i) waves are not reflected from the walls accept microwaves / radar for waves do not accept bounce / deflected etc for reflected or only waves (reflected) from the device are detected accept to stop reflected waves affecting results different types (of device) can be compared fair test is insufficient accept idea that only one variable is then changed Page 24 of 38
(iii) so (measurements / results / scientists) are not biased towards one type / manufacturer of device/s accept to avoid bias accept so they are not biased (e) (i) any two from: if temperature is mentioned rather than angle a maximum of mark can be scored (for any angle) A values < B values or converse eg B values are higher / better / stronger A values increase with (increasing) angle accept weakest at 0 strongest at 5 values go up is insufficient B values decrease with (increasing) angle accept strongest at 0 weakest at 5 values go down is insufficient A values do not vary as much (as B values) 2 D mark is for the reason reason cannot score if D is not chosen values are always over 2(.0) [0] M5. (a) two rays drawn from the bulb and reflected by the glass angle I = angle R judged by eye allow mark for one incident and reflected ray even if angle I doesn t equal angle R 2 at least one arrow drawn in correct direction any conflicting arrows negate this mark ignore any arrows drawn on construction lines behind the glass Page 25 of 38
position of image correct judged by eye image is formed by virtual / imaginary rays crossing accept construction lines only show where the light seems to come from accept the image is behind the glass / mirror accept image is seen through the glass / mirror accept (real) rays of light do not pass through the image accept (real) rays do not cross accept the image is a reflection (of the object) accept the image is formed by reflection do not accept a virtual image can t be formed on a screen do not accept the object / image is reflected [5] Page 26 of 38
M6. (a) (i) any two from: travel at the same speed (through a vacuum) accept travel at the speed of light accept air for vacuum can travel through a vacuum / space do not accept air for vacuum transfer energy can be reflected can be refracted can be diffracted can be absorbed can be transmitted transverse accept any other property common to electromagnetic waves accept travel at the same speed through a vacuum for both marks do not accept both radiated from the Sun 2 infra red both required for the mark radio(waves) accept IR for infra red 2 400 000 000 correct transformation and substitution gains mark ie or an answer of 24 000 000 gains mark either 2 400 000 khz or 2 400 MHz scores 3 marks but the symbol only scores the 3 rd mark if it is correct in every detail 2 hertz accept Hz do not accept hz (c) (i) presented (scientific) evidence / data do an experiment / investigation is insufficient Page 27 of 38
to find out if there is a hazard (or not) accept to find out if it is safe accept not enough evidence to make a decision not enough evidence is insufficient [8] M7. (a) (i) vibrate / oscillate accept a correct description move is insufficient 336 allow mark for correct substitution, ie 420 0.8(0) provided no subsequent step shown 2 (i) frequency longer than 0.8m (iii) Doppler [6] M8. (a) (i) red-shift accept Doppler (effect) the Universe is expanding (iii) N Why was the Universe created? [4] M9. (a) frequency / pitch decreases accept wavelength increases accept it / the note becomes deeper / lower it / the note decreases is insufficient quieter is neutral (i) (moving) loudspeaker Page 28 of 38
change in sound as loudspeaker moves away models can help to explain an effect or theory (c) big bang [5] M0. (a) Y accept cannot be X as size is increasing shows Universe expanding this scores if Y or Z is chosen accept exploding outwards from a (very small) point this only scores if Y is chosen accept from zero (size) answers in terms of planets negate the last two mark points (i) both the big bang and steady state theories (new) evidence that supports / disproves a theory accept proves for supports or (new) evidence not supported by current theory accept there may be more evidence supporting one (theory) than the other (theory) accept new evidence specific to this question eg measurement of CBR or some types of star only found in distant parts of Universe (steady state suggests should be same throughout Universe) [5] Page 29 of 38
M. (a) any three from: red-shift shows galaxies are moving away (from each other / the Earth) more distant galaxies show bigger red-shift or more distant galaxies show a greater increase in wavelength accept correct reference to frequency in place of wavelength (in all directions) more distant galaxies are moving away faster accept (suggests) universe is expanding suggests single point of origin (of the universe) 3 (i) (radiation produced shortly after) Big Bang accept beginning of time / beginning of the universe for Big Bang any one from: can only be explained by Big Bang existence predicted by Big Bang provides (further) evidence for Big Bang ignore proves Big Bang (theory) ignore reference to red-shift (iii) increase accept becomes radio waves universe continues to accelerate outwards accept as universe continues to expand or greater red-shift [7] M2. (a) (i) Universe began at a (very) small (initial) point it refers to Universe explosion sent matter outwards or explosion causing Universe to expand accept gas / dust for matter accept rapid expansion for explosion Page 30 of 38
light shows a red shift owtte the term red shift on its own does not score a mark galaxies moving away (from the Earth) it refers to light they refers to galaxies accept star for galaxy do not accept planet for galaxy check reliability / validity of data accept check data accept collect more data amend theory or discount the data accept replace old theory with new theory (c) answer involves (religious) belief or no / insufficient evidence accept it cannot be tested [7] Page 3 of 38
E. (a) (i) Most students realised that traffic lights communicate using visible light. Most students thought that satellites used radio waves for communication rather than microwaves. About two thirds of the students correctly identified position J as being gamma rays. (c) (i) Most students correctly identified B as showing the wavelength. Most students knew that the wavelength of infrared waves is shorter than the wavelength of radio waves. (d) (i) Most students realised that scientists were trying to find out if using a mobile phone is harmful to health, although a significant proportion thought that it was to find out if mobile phones give out radiation. Although many students were able to score both marks in this question, about half of them only scored one mark, either for explaining that mobile phone X would cause a smaller amount of energy to be absorbed by the head or that mobile phone X would be safer. Some students thought that the SAR value showed how much energy the phone itself absorbed. E2. (a) Most students thought that the image would be at position B rather than position C. Most students could show a ray reflected from the mirror but not all were able to show it reflecting at an appropriate angle. Although most students put arrows on the rays, in many cases these showed the light to be emerging from the eye. It was pleasing to note that the great majority of students used a ruler to draw the rays. (c) Most students knew that the image was virtual. The most common incorrect answer was imaginary. Page 32 of 38
E3. (a) About three-quarters of students could correctly identify a region of compression in the spring. (i) There were many excellent responses to this question scoring both marks. However, a significant number of students failed to score both marks because of the careless way in which the lines had been drawn. Examples included angles being nowhere near equal, large gaps between the ray and the reflecting surface and lines starting and finishing large distances from the speaker and the sound sensor. (iii) (iv) Over half of students were able to suggest a suitable reason for the reading on the sound level meter going down. About two-thirds of students correctly chose 'makes the sound louder'. The calculation of the speed of sound was generally well done with three-quarters of students scoring both marks. (c) A surprisingly large number of students did not know that a reflected sound is called an echo. Almost a fifth of students did not attempt this question. (d) (i) Half of the students correctly chose the frequency range from 250 Hz to 750 Hz. Only the better students realised that the reason why curtains would be better than carpet is because curtains reflect less sound. Many thought that carpet would be a better choice, in spite of the fact that in the stem of the question they were told that curtains would be better. In some of these cases, it was clear that students thought that reflection of sound was a good thing. In some cases, students thought that because the line for carpet on the graph was higher than the line for curtains, it must therefore be better. Very few students could make a sensible reference to the frequencies shown on the x-axis. Some students thought that curtains and carpet were able to change the frequency in different ways. Page 33 of 38
E4. (a) This was a poorly answered question. Many candidates wrote about the uses of the two waves instead of the way in which the waves themselves were different or simply said that the wavelength / frequency was different without stating how. (c) Again a poorly answered question, with many candidates believing that the waves would travel at different speeds. Just over one-fifth of candidates did not attempt this part question. Only a small percentage of candidates scored both marks for this question, as the majority of candidates failed to refer to what happened to the microwaves when they reached the plastic casing. Of those who did refer to this, many were confused between absorption and transmission. Many candidates gained one mark for stating that the microwaves would be reflected, but some candidates lost this mark because they used the word bounce or deflect instead of reflect. (d) (i) Very few correct answers were seen to this question. Most candidates thought that the waves had to be absorbed in order to stop them escaping from the room and then possibly harming people. (iii) A very poorly answered question, with the majority of candidates simply stating that this was in order to make it a fair test. Only the better candidates realised that this was in order to eliminate any possible bias, but many candidates simply repeated their fair test answer. (e) (i) Just over half of the candidates were able to score at least one mark here, although some of the weaker candidates thought that as the measurement was in degrees it must be referring to temperature. This question was correctly answered by about half of the candidates. E5. (a) Very few students were able to locate the correct position of the image. Many students were able to draw one ray from the object to the glass and show it reflecting towards the eye, but in most cases, the angle of incidence was significantly and obviously different to the angle of reflection. If arrows were drawn on the rays, they were mostly shown in the correct direction. A second ray from the object and construction rays behind the glass were rarely seen. Less than a tenth of students achieved three or four marks. Very few answers explained that the image is formed by virtual / imaginary rays crossing. Page 34 of 38
E6. (a) (i) It appeared that the term.properties. was not understood by many candidates, and answers giving uses of the waves were more frequently seen. Candidates should be aware that they do not generally gain credit for repeating information which they have been given in the question, so saying that both waves were electromagnetic or that both could be used for communications did not score any credit. This question was correctly answered by just under three quarters of candidates, although some candidates gave.visible light and microwaves. as an answer, failing to realise that the question had already referred to these waves. Although a large number of candidates were able to transform the equation and substitute values, the majority failed to convert the wavelength from centimetres. The majority of candidates either did not read that they also had to give the unit, or perhaps did not know what the unit was, but those who gave the unit usually did so correctly. (c) (i) Many candidates seemed to have the correct idea but failed to express themselves correctly. A common incorrect answer was to suggest that the politician should carry out an experiment. A surprisingly large number of answers indicated that candidates had read the question as asking why there was no need for further research. Other answers included terms such as bias, valid and accurate that did not answer the question. E7. (a) (i) About half of the students knew that sound waves cause the air particles to vibrate. A common answer that was insufficient to gain a mark was simply to say that sound waves caused the air particles to move. The majority of students could correctly complete the calculation to find the speed of the waves. The most common mistake was to divide 420 by 0.8 instead of multiplying. (i) Fewer than half of the students knew that it is the frequency that determines the pitch of a sound. The most common incorrect answer was amplitude. (iii) Fewer than half of the students knew that the wavelength would be longer than 0.8 m. Most students could identify the effect as being the Doppler effect. E8. (a) (i) About half of the students knew that this observation is called red-shift. (iii) The great majority of students knew that the observation gives scientists evidence that the Universe is expanding. The most popular incorrect answer was that light can be stretched. Most students correctly identified graph N as representing the relationship between observed increase in wavelength and distance from Earth. Most students knew that the question Why was the Universe created? is one that scientists are unable to answer. The most popular wrong choice was How fast does light travel through the Universe? Page 35 of 38
E9. (a) The sound becoming quieter was a common incorrect response. No credit was given for 'it decreases' or 'the note decreases' since it was not clear enough to what the student referred. Correct answers were rare. (i) Most students realised that the moving loudspeaker represented the moving galaxy. However, the second mark was rarely gained. Responses such as 'the teacher' or 'the class' were the most common. Even those who identified the speaker moving away usually neglected to mention the change in the sound. The majority of the students gained this mark. (c) Apart from the odd suggestion such as 'evolution' or 'Doppler effect', the vast majority of students were able to answer this correctly. E0. (a) Most students gained some credit here, mostly by correctly identifying Y as the correct graph. Many students then went on to write that this graph showed the Universe expanding but fewer were able to state that the Universe had started at a point. A significant number of students confused the Universe with the Solar System or the Earth, and therefore could only score the first mark. (i) Only a minority of students thought that red-shift provides evidence for both the big bang and steady state theories. Those students that scored the mark in this question tended to answer in terms of one theory having more evidence that the other. The question was a general one about the support of the scientific community for a particular theory and those that answered in these terms tended to be more successful than those who attempted to discuss the evidence for the big bang and steady state theories in particular. E. (a) This was not well answered with just over a tenth of students scoring all three marks. Just over a quarter of students scored two out of the three marks, usually for indicating that red-shift shows that galaxies are moving away from each other or from the Earth and for the statement that the Universe is expanding. Common errors were that the Earth is expanding or that planets are moving away from each other. Also 'galaxies moving towards the red end of the spectrum' was often seen. (i) About two-thirds of students could give the origin of CMBR to score this mark. (iii) Only a third of students scored this mark. A lot of responses were claiming that CMBR was proof of the Big Bang theory. About two-thirds of students were able to state that the wavelength would be likely to increase, with about half of these students going on to give a correct reason. Page 36 of 38
E2. (a) (i) Considering the regularity of this or a similar question it seems surprising that over half of the candidates scored zero. Many of these candidates just refer to the creation of the earth or the solar system. Many candidates referred to red shift, although quite a few seemed to think that the galaxies themselves undergo red shift or that the galaxies were turning red. (c) There seemed to be some confusion between the terms theory and dat, with a large number of candidates reading the question as a new theory having been stated. Just over half of the candidates scored the mark with references either to the fact that there is no evidence or the question being a matter of philosophical or religious beliefs. Page 37 of 38
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